The electrochemical behaviour of solutions of molten ternary alkali carbonate mixture equilibrated with carbon dioxide-water mixtures at 460°C

White, S. H.; Twardoch, U.M.

doi:10.1016/0013-4686(84)87074-7

Cited by 22 publications

(18 citation statements)

References 18 publications

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“…10 shows an almost exponential decrease of the current function with the scan rate, which is consistent with an electrode reaction coupled with a following chemical reaction (EC mechanism). As reported in (15,16) On the basis of these CV results, it can be concluded that the bicarbonate reduction process takes place through a rather complex mechanism, which is coupled with chemical reactions and adsorption processes. Although the bicarbonate-assisted water reduction process can be conveniently regarded as an EC mechanism (15,16), however, a more refined treatment should also consider the effect of the preceding chemical reactions (eqs.…”

Section: Resultsmentioning

confidence: 75%

“…As reported in (15,16) On the basis of these CV results, it can be concluded that the bicarbonate reduction process takes place through a rather complex mechanism, which is coupled with chemical reactions and adsorption processes. Although the bicarbonate-assisted water reduction process can be conveniently regarded as an EC mechanism (15,16), however, a more refined treatment should also consider the effect of the preceding chemical reactions (eqs. [6]- [7]), leading to the bicarbonate formation.…”

Section: Resultsmentioning

confidence: 75%

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A Novel Process for Solar Hydrogen Production Based on Water Electrolysis in Alkali Molten Carbonates

Frangini¹,

Felici²,

Tarquini³

2014

ECS Trans.

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In order to evaluate the technical feasibility of a novel solar hydrogen production process, the molten carbonate electroreduction behavior of water in the range 505-600°C was examined in this paper. Reaction kinetics and mechanism of the water reduction process was elucidated by using galvanostatic polarization methods and cyclic voltammetry. Two different water electrolysis mechanisms were found to be active in this temperature range, involving either bicarbonate or hydroxide anions as intermediate species, much depending on reaction conditions and melt temperature. Due to lack of knowledge, the bicarbonate mechanism was studied in detail. In accordance with a rapid thermodynamic decrease of bicarbonate stability above the 500°C, the voltammetric data showed a transition from bicarbonate to hydroxide mechanism at around 550°C. The results also indicated that water electrolysis in alkali molten carbonates can be conveniently operated in the 500°C area, where the relatively higher bicarbonate stability may enable a more rapid reaction than at higher temperatures. IntroductionHigh temperature electrolysis of water has a tremendous potential in enabling a cost-effective and sustainable production of hydrogen by using renewable heat and electricity from concentrating solar thermal (CSP) plants (1). Most efforts in this research area are currently directed towards investigating solid oxide electrolysis cells (SOECs) based on fuel cell technology (2,3), although this approach is not optimal for thermal integration with CSP plants because of electrolysis temperatures (i.e., above 800°C) significantly exceeding those of most solar heat storage fluids. In order to reduce the temperature gap with current solar thermal fluids, development of electrolysis processes within the 500-600°C range would be a desirable option. In this context, molten salts could be seen as an ideal medium to lower process temperatures with respect to solid oxide electrolyzers since overall ionic conductivity and transport numbers of liquid salts are usually higher than solid-type electrolytes. Recently, alkali 10.1149/06122.0013ecst ©The Electrochemical Society ECS Transactions, 61 (22) 13-25 (2014) 13 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 142.58.129.109 Downloaded on 2014-11-17 to IP molten carbonate salts have gained a return of attention as versatile electrolytes for conducting electrochemical conversion processes of mineral ores and CO 2 gas at moderate temperatures (4,5).In this context, molten carbonate electrolysis (MCE) to produce hydrogen from water is another process that has been recently mentioned in literature (2), although no systematic studies on this process have been so far conducted. Only very recently, the feasibility of a MCE process for hydrogen production has been demonstrated on laboratory scale experiments in the 600-675°C range using a Molten Carbonate Fuel Cell (MCFC) operated in a reverse (electrolysis) mode (6). Interestingly, the a...

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Section: Resultsmentioning

confidence: 75%

Section: Resultsmentioning

confidence: 75%

A Novel Process for Solar Hydrogen Production Based on Water Electrolysis in Alkali Molten Carbonates

Frangini¹,

Felici²,

Tarquini³

2014

ECS Trans.

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“…Interaction between nanosized ceria and water seems to be even stronger than in the case of larger oxide particles 32. Hydrogenated species are also formed in molten carbonates exposed to water or hydrogen 33, 34. Thus, the presence of various types of hydrogenated species in composites of ceria and molten alkaline carbonates is undoubtedly expected 19.…”

Section: Resultsmentioning

confidence: 99%

Compositional and microstructural effects in composite electrolytes for fuel cells

Ferreira

Saradha

Figueiredo

et al. 2011

Int. J. Energy Res.

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Composite ionic conductors were produced by combination of alkaline carbonates with various ceramic oxides, including ceria, zirconia and alumina. The adopted mechano-thermal processing routes originated materials with the same nominal composition but with significantly different microstructures. The electrical performance of these composites, studied by impedance spectroscopy, showed the relevance of the mixed carbonate phase on the transport properties, but also unexpected composite effects. The role of grain size on the electrical performance could not be isolated from the possible influence of alkaline metal rich interfacial layers (ceramic/carbonate) consisting of nanosized 1D crystals. Modest electrode impedances in open air experiments are coherent with the coexistence of various charge carriers. The known interaction of major composite constituents and minor secondary phases with water might explain the presence of additional charge carriers.

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“…Redistribution subject to ECS terms of use (see 138.251.14 35. The two noteworthy features highlighted by the data are the large shifts in the second ) unless CC License in place (see abstract).…”

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confidence: 86%

The Formation of Menisci/Films on Gold Electrodes Immersed in Molten Carbonates and Their Effect on Cyclic Voltammetric Measurements

White¹,

Twardoch²

1988

J. Electrochem. Soc.

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The study of redox reactions which involve gaseous reagents is important in the development of fuel cells and gas scrubbing eleetrolyzers. Oxygen electrodes are of particular concern in molten alkali carbonate fuel cells. The reported data for this redox system have generated some divergence of opinion concerning the mechanisms and kinetics particularly with precious metal substrates. The results of cyclic voltammetric studies at gold electrodes where menisci have been deliberately formed, show that the voltammetric response is modified by the presence of the meniscus. Previous data obtained at improperly shielded electrodes Such as wires or flags must be reassessed in the light of the reported resuits.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 138.251.14.35 Downloaded on 2015-05-29 to IP Vol. 135, No. 4 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 138.251.14.35 Downloaded on 2015-05-29 to IP

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The electrochemical behaviour of solutions of molten ternary alkali carbonate mixture equilibrated with carbon dioxide-water mixtures at 460°C

Cited by 22 publications

References 18 publications

A Novel Process for Solar Hydrogen Production Based on Water Electrolysis in Alkali Molten Carbonates

A Novel Process for Solar Hydrogen Production Based on Water Electrolysis in Alkali Molten Carbonates

Compositional and microstructural effects in composite electrolytes for fuel cells

The Formation of Menisci/Films on Gold Electrodes Immersed in Molten Carbonates and Their Effect on Cyclic Voltammetric Measurements

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